This invention relates to heat pump air conditioning involving a multiplicity of zones to be conditioned on a scheduled basis or continuing basis as may be required. Heretofore, full capacity heat pumps have been employed for this purpose, their capacity being determined according to the zone space that is to be conditioned, and without regard to the shut-down time that is to be expected. When central air conditioning systems are employed the total of the zone space requirements must be considered and conditioning equipment adequate for the whole is normally provided, again without regard to the shut-down time which inherently occurs as conditioning requirements vary from zone to zone, and from time to time. Therefore, full capacity equipment for multi zone air conditioning has not been altogether cost effective, because the full capacity equipment cannot be operated to full capacity on a full time basis. Accordingly, it is a general object of this invention to provide a Multi-Zone Variable Air Volume Hydronic Heat Pump System for air conditioning in which capacity effective averaging is employed in the selection of heat pump capacities and in which the heat pumps are operated on a full time schedule with their outputs used and/or stored as excess energy for subsequent use in the air conditioning process.
It is an object of this invention to advantageously employ a multiplicity of heat pumps of the same or varied capacities, all selected on a capacity effective basis. In accordance with this invention, a capacity effective averaging basis is the energy required to operate during a scheduled period, usually for a full day; for either air conditioned cooling or air conditioned heating. A feature of this invention is the banking of excess energy acquired by operation of the multiplicity of heat pumps on a full time schedule. In practice, that schedule may be a full twenty four hour day, or preferably a lesser period in order to provide air conditioning during occupancy of the zones involved. For example, an office building occupied only during business hours need not be air conditioned throughout the off-time hours; taking into account a preconditioning period that may be desired etc. Also conditioning requirements will vary according to season, and all of which can be adjusted for in the operation of this system.
It is an object of this invention to absorb and store excess energy, both in the form of heat and cold, from conditioned air produced by the multiplicity of heat pumps and not required at the time for zone conditioning. For example, there will be times when zone conditioning requirements are reduced, or do not exist at all. In practice, there is both hot water and chilled water storage, from which the chilled condition fluid can be drawn and used for subsequent air conditioning. Each, the hot and the chilled water-energy storage means, is a closed circuit with its control and pump means with make-up means and a compression tank. Excess heat is dissipated by a cooling tower, while insufficient heat is supplemented by a water heater or boilder.
It is an object of this invention to provide a control means whereby variable air volume flow restriction causes operation of either of the aforementioned hot water or chilled water storage means. With this invention, a flow sensor (pressure) at the air supply or inlet of the heat pump determines operation of either the hot water or chilled water storage means.
It is an object of this invention to provide a by-pass for the heat pump air circulation and control means therefor whereby the heat pump operates at full capacity at all times, when the systen is in operation, with all or a portion of its conditioned air delivered to the zone space, and alternately with all or a portion of its conditioned air by-passed for conservation of energy by the aforesaid hot water or chilled water storage means.
A widely used system for the control of supply air to the zone space being conditioned is the Variable-Air-Volume (VAV) system, wherein a by-pass with a pressure responsive damper recirculates conditioned air that is restricted by zone space dampers. Aside from the aforementioned improvements in the conservation of energy by banking conditioned liquid, there is the problem of air quality which arises when employing VAV systems. That is, as and when the zone space dampers are modulated down (toward closed), the usual filtration through the return air duct becomes less effective, since the return air volume decreases, there being no air quality change through the recirculation duct. Consequently, the reduced volume of supply air is inadequately filtered and permits the quality of zone space air to deteriorate. Accordingly, it is an object of this invention to provide super-filtration of recirculation air in the Variable-Air-Volume (VAV) system, whereby the reduced discharge of supply air adequately improves the air quality of the zone space air, as and when the zone space dampers modulate. Air quality improvement then becomes inherent. With the present invention, there are primary and secondary air filters; a primary air filter in the return air duct, and a secondary air filter in the recirculation VAV duct. Initial one time filtration occurs through the primary filter, while repeated, partial or additional filtration occurs through the secondary filter. A higher quality filtration is thereby attained, super-filtration, for restricted discharge at reduced volume as supply air by the zone space dampers.